White-Box Cryptography Algorithm Design And Implementation Of SMS4

In recent years, with the development of cipher attacks, the traditional black-box cryptographic attack model becomes more and more fragile. Unlike traditional cryptographic attack model, white-box attack model gives attackers more capacities, in White-Box Attack Context, the attacker can control cryptographic algorithms over the software and have the ability to observe and modify the running data. The cryptographic that can resist White-Box Attack Context is called White-Box Cryptography. The objective of designing White-Box Cryptography is to hide the key information, prevent attackers from obtaining the key in White-Box Attack Context effectively. Therefore, it is important to design safe and efficient White-Box Cryptographic algorithm.SMS4 algorithm is the first block cipher algorithm for wireless LAN products,which is widely used in our country. The research goal of this paper is to design White-Box SMS4 and realize White-Box SMS4 cryptography algorithm with software platform. The main research contents include:Firstly, this thesis describes White-Box Cryptography, and it’s design methods and safety assessment, analyzes features of White-Box SMS4 implementation by Xiao Yaying, studies a attack to the scheme by Lin Tingting et al and reasons for the success.Secondly, this thesis provides two improved algorithms of Xiao-White-Box SMS4 algorithm, and analyzes the efficiency and safety of the improved algorithm. The first improved algorithm reduces four lookup tables to two, saving the number of look-up tables, but it increases the extra space. On the other hand, in terms of safety, the attack time complexity can be increased by at least 2-fold. The second improved algorithm to Xiao-White-Box SMS4 algorithm on the one hand, it simplifies parameteri jP?、i4P?? andi4P??, saving the computational complexity in the calculation of the parameters,and it’s white-box diversity and white-box ambiguity can meet certain security; on the other hand, it increases an external encoder, making the entire algorithm integrity.Finally, this thesis provides the implementation of White-Box SMS4 which is based on the second improved algorithm this thesis gived, and implements a visual encryption applications on MFC; this thesis also provides the compare of the implementation efficiency, speed and security between White-Box SMS4 and Black-Box SMS4 algorithm. The White-Box SMS4 algorithm can protect the keyinformation in White-Box Attack Context. White-box SMS4 algorithm can effectively protect the key information in White-Box Attack Context, and broaden the application field of SMS4 algorithm.